1. Field of the Invention
This invention relates to an opening/closing device for a pipe file binder.
2. Brief Description of the Prior Art
Among many kinds of file binders, the present invention relates to a comparatively thick (or heavy) file using a pipe, i.e., a pipe file binder in which a pair of cover plates (or closure plates) mounted on opposite longitudinal sides of a binder base can be opened and closed, and attached and detached in opposite directions.
Japanese Utility Model Publication No. Hei 3-4551, Japanese Laid-Open Utility Model Publication No. Hei 3-87286 and Japanese Laid-Open Patent Publication No. Hei 4-341898 disclose file binders of this type. However, these utility models and invention have the following shortcomings.
The above-mentioned Japanese Utility Model Publication No. Hei 3-4551 has such shortcomings that since engageable slip plates are mounted in side plates of a rotary member, a spine portion becomes thicker and therefore, a storage rack cannot be used effectively.
The second-mentioned Japanese Laid-Open Utility Model Publication No. Hei 3-87286 has such shortcomings that since shafts are pivotally supported on upper side portions of opposite side plates of a base and projection buttons extending through the side plates, respectively, are formed on inner slide pieces, a base plate portion of the binder becomes extremely thick and a surplus width is formed in a cover sheet direction.
The last-mentioned Japanese Laid-Open Patent Publication No. Hei 4-341898 indeed has successfully obviated the shortcomings had by the first and second mentioned prior publications. However, it again has another shortcoming in that since an engageable guide shaft is located under a group of sheets of paper, the user often finds it difficult to insert his/her finger to operate the guide shaft in a somewhat awkward manner.
Other publications such as Japanese Utility Model Publication No. Sho 52-52660, Japanese Utility Model Publication No. Hei 2-32466 and Japanese Laid-Open Utility Model Publication No. Hei 2-64081 are also known. However, the devices disclosed by those publications are all found to be difficult to operate smoothly and therefore, hardly put into actual practice.